DE-102025146296-A1 - X-ray detector, material for X-ray detection and its use for X-ray detection, as well as methods for its manufacture

Abstract

The invention relates to X-ray detectors comprising X-ray detector materials whose material composition includes salts of sulfonium cations, wherein the anions are preferably bismuth halides or bismuth-silver halides, in particular iodides. The invention further relates to the X-ray detector materials and their use for X-ray detection, together with a method for their production.

Inventors

• Allan Starkholm
• Olena Maslyanchuk
• Eva Unger
• Lars Kloo
• Per Henrik Svensson

Assignees

• Helmholtz-Zentrum Berlin für Materialien und Energie Gesellschaft mit beschränkter Haftung

Dates

Publication Date

20260513

Application Date

20251110

Priority Date

20250115

Claims (9)

1. X-ray detector comprising an X-ray detector material comprising at least one salt of sulfonium cation and bismuth halides or bismuth silver halides as anions.
2. X-ray detector after Claim 1 , characterized in that the X-ray detection material comprises at least [R 3 S] 6 Bi 8 I 30 or [R 3 S]AgBil 5 , wherein R is at least one of the group consisting of trimethylsulfonium [Me 3 S] + , triethylsulfonium [Et 3 S] + , tripropylsulfonium [n-Pr 3 S] + , triisopropylsulfonium [i-Pr 3 S] + , tributylsulfonium [n-Bu 3 S] + , dimethylethylsulfonium [Me 2 EtS] + , methyldiethylsulfonium [MeEt 2 S] + , methyl-ethylpropylsulfonium [MeEtPrS] + , methyl-di(n-propyl)sulfonium [Me(n-Pr) 2 S] + , methyl-di(n-butyl)sulfonium [Me(n-Bu) 2 S] + , ethyl-di(n-propyl)sulfonium [Et(n-Pr) 2 S] + , methyl-ethyl-isopropylsulfonium [MeEt(i-Pr)S] + and methyl-ethyl-butylsulfonium [MeEt(n-Bu)S] + .
3. X-ray detector after Claim 1 or 2 , characterized in that the X-ray detector material comprises at least [Et 3 S] 6 Bi 8 I 30 or [Et 3 S]AgBil 5 .
4. X-ray detector according to one of the preceding claims, characterized in that the X-ray detector material is in pellet form.
5. X-ray detector after Claim 4 characterized in that the pellet has a thickness in the range of 0.5 to 5 mm.
6. X-ray detector after Claim 1 , 2 or 3 characterized in that the material exists as a single crystal.
7. Material for X-ray detection comprising at least one salt of sulfonium cation and bismuth halides or bismuth silver halides as anions.
8. Use of material for X-ray detection comprising at least one salt of a sulfonium cation with bismuth halides or bismuth silver halides as anions in an energy range of X-rays between 100 eV and 120 keV, in particular 100 eV and 40 keV.
9. A process for producing pressed powder pellets comprising at least one salt of a sulfonium cation and bismuth halides or bismuth-silver halides as anions, by the following steps: a. Providing powdered BiI 3 , Agl and sulfonium halide as precursors in stoichiometric amounts, b. Mixing or milling the powders, c. Pressing the mixed or milled powders from step b. at a pressure in the range of 0.2 to 1.2 GPa for a period of time in the range of 5 seconds to 600 seconds.

Description

background High-performance, long-life semiconductor X-ray and gamma-ray detectors (X/y detectors) are well-established technologies used in medical imaging, non-destructive testing, security technology, the nuclear industry, and scientific research. Materials such as amorphous selenium (a-Se) and cadmium(Zn)Te, as described by A. Owens, are commonly used for the direct conversion of X-rays and gamma rays. These materials are known for their complex crystal growth processes and operational requirements, such as strong electric fields. Particularly in medical imaging, there is a significant need for detectors with improved sensitivity and lower limits of detection compared to the current state of the art, as these would allow for the use of lower radiation doses and thus reduce patient exposure. Key performance indicators (KPIs) for X-ray detectors include sensitivity, limit of detection (LoD), mobility-life product (µτ), and resistivity. Sensitivity refers to the detector's ability to convert X-ray photons into an electrical signal, while the limit of detection (LoD) indicates the minimum detectable radiation above the background noise. Since 2013, there has been a resurgence in the field of novel X-ray detector materials, following the description of lead-based metal halide perovskites as promising alternatives for X-ray detection due to their high resistance, excellent µτ products, high atomic numbers (Z), and ease of synthesis, as outlined by Y. He et al. However, their instability under ambient conditions remains a significant limitation (S. Shrestha). An X-ray detector material within the meaning of the invention is any solid material, in particular any semiconductor, which is capable of converting X-rays either into electrical charge (electronic signal) or into photons that can be detected. Organic-inorganic hybrid materials based on bismuth (Bi-based) have proven to be a promising alternative, as they offer superior thermal and moisture stability compared to lead-based perovskites. Y. Xu et al., M. Daum et al. These materials are frequently synthesized using low-temperature and non-vacuum methods, making them a cost-effective option. Bi halides, in particular, exhibit favorable band gaps (1.8–2.5 eV) and high atomic numbers (Z = 83 for Bi, Z = 53 for I), contributing to low thermal noise and high X-ray absorption. Among the best - studied bi halides is Cs₂AgBiBr₆ , a double perovskite known for its indirect band gap, long charge carrier lifetime , and excellent stability. Cs₂AgBiBr₆ has been investigated as an X-ray detector in the form of single crystals (W. Pan), films (YC Kim), and thick pellets (B. Yang), exhibiting sensitivities up to 1974 µC·Gy air⁻¹ · cm⁻² in single-crystal detectors. Furthermore , other bi-based materials such as MA₃Bi₂I₉ , BiOl , Cs₃Bi₂I₉ , and Rb₃Bi₂I₉ have shown promising properties, with reported sensitivities up to 10620 µC· Gy air⁻¹ · cm⁻² for MA₃Bi₂I₉ in single - crystal form. Single crystals (SCs) generally outperform amorphous or polycrystalline materials due to their superior crystal quality, absence of grain boundaries, and minimal defects (Y. Song et al.). However, scaling up single crystals for practical applications remains a challenge due to the difficulty of growing large crystals using conventional techniques such as the Bridgman and Czochralski methods, which are both time-consuming and expensive, thus limiting their scalability for practical use. In contrast, polycrystalline pellets (cylindrical bodies of densified polycrystalline material) represent a practical alternative for flat-panel X-ray detectors because they can be produced quickly and cost-effectively by hydraulic compression, enabling the fabrication of thick X-ray detector materials essential for effective X-ray absorption. Although pellets generally exhibit lower performance than single crystals due to the presence of grain boundaries, which are known sites of recombination loss, recent studies have shown that bismuth-based materials in pellet form nevertheless exhibit promising sensitivities and levels of detection (LoD), often outperforming traditional materials such as α-Se and Cd(Zn)Te. Furthermore, lead-based perovskites such as MAPbI₃ in pellet form have shown comparable results, further encouraging research in this area, despite the materials' environmental and health risks. An X-ray detector according to the invention comprises at least an X-ray detector material and any means for converting an electronic signal or light from the X-ray detector material caused by the incidence of X-rays. The simplest form of an X-ray detector consists of an X-ray detector material between two electrically contacted Metal plates that transmit any signal from the material and may apply a bias voltage. The electrodes can be made, for example, from a material belonging to the group consisting of Au, Ag, Al, Pt, Pd, In, C, graphene, graphite, carbon nanotubes (CNTs), carbon black, ITO (indium tin oxide), FTO